The inspection of tubular members used in the oil and gas drilling industries is primarily concerned with locating and removing defects in the members. The characteristics of a defect, e.g. size, shape and orientation, establish whether the tubular member could be used in the oil and gas drilling industries.
When a defect is located on a surface of the tubular member, the defect can be visually characterized and probed for decisions as to whether removal of the defect is necessary and whether removal is feasible by grinding or other means. However, when a defect is located within the tubular member, the defect is not easily characterized or quantified. Tubular members are usually discarded when defects are not adequately characterized or quantified.
Prior ultrasonic inspection devices have used sonic beams to locate defects in tubular members. For example, U.S. Pat. No. 4,217,782, assigned to W. C. Lamb, describes an ultrasonic inspection device for inspecting tubular members for the oil and gas drilling industries. The described device employs two pairs of line-focused transducers that transmit sonic beams having a rectangular beam cross-section of about 3/4 inch in length. A first pair of the transducers transmits sonic beams longitudinally into the member to detect transverse defects. The second pair transmits sonic beams transversely into the member to detect longitudinal defects. The transducers in each pair transmit sonic beams in opposite directions. Two additional transducers monitor the wall thickness of the tubular member.
Longitudinally transmitted and transversely transmitted sonic beams are used for the inspection of tubular members as some defects are visible to only one or the other. In fact, some defects are invisible to both longitudinally and transversely transmitted sonic beams. In at least one instance, the ultrasonic inspection device of U.S. Pat. No. 4,217,782 has been modified to include four spot-focused transducers that transmit sonic beams having a circular beam cross-section obliquely through the tubular member. Also, a pair of transducers that transmit in opposite directions is often used to detect defects in tubular members as described in U.S. Pat. No. 3,289,468 because a given defect may be invisible to a transducer looking at it from one direction and visible to a transducer looking at it from the opposite direction.
The characterization of a defect for size, shape, and orientation generally requires the transmission of sonic beams from several different directions followed by the receiving of beams reflected from the defect. In the past, reflected beams from one transducer have been received by several transducers to detect some of the defects, as described in U.S. Pat. No. 3,332,278. However, the ultrasonic inspection of a tubular member using multiple receiving transducers as used in the past has had the difficulty of detecting defects, and characterizing them, for pipes having different external diameters and different wall thicknesses.
Thus, there has been a need for an ultrasonic inspection device that is capable of characterizing defects in tubular members.